Process for preventing the spoilage of canned foods.



UNITED STATES PATENT OFFICE.

EDWARD W. DUCKWALL, 0F ASPINWALL, PENNSYLVANIA"- PROCESS FOR PREVENTINGTHE SPOILAGE 'OF CANNED FOODS. 7

No Drawing.

To all whom it may concern Be it known that I, EDWARD W. Doon- WALL,citizen of the United States, residlng ,at Aspi'nwall, in the county ofAllegheny and State of Pennsylvania, have invented certain new anduseful Improvements in Processes for Preventing the Spoilage of CannedFoods, of which the following is a specification.

This invention relates to an improved process for preventing thespoilage of canned food, and has for its primary object a provision of'a simple, effective and inexpensive process, whereby the destruction ofliving, previously undestroyed bacteria will be absolutely assured, sothat the food may be indefinitely preserved in an edible condition.

The invention further has for its object an improved process whereby theabove result may be successfully accomplished without deleteriouslyaffecting the hermetically sealed foods in regard to their flavor andquality.

Before proceeding with a detailed description of my improved process, astatement regarding the ordinary methods of sterilization employed bycanners will be given to materially assist in disclosing the advantagesof my process and thus arriving at a clear and full understanding of itsefficiency in practical use.

All canners of food products endeavor to use a sterilizing process whichwill consume as little time as possible, and with a sterilizing heat nohigher than thought to be necessary, or as close to the danger line aspossible, because over-heating of the foods usually injures theirflavor, therefore the sterilizing temperatures are kept as low aspossible with considerable guess-work as to the efficiency, usuallybasing the time and temperature on past experience as an index or arule, which very frequently does not prove adequate. In case the primarysterilizing process has been insufficient to secure completesterilization, some of the bacteria in spore form will survive, and theheat used in the primary process-has a tendency to start the developmentof the undestroyed spores of these bacteria.

All canned foods having an acidity of less than one-quarter of one percent. are liable to spoilage, if not sufficiently sterilized in theprimary process, by the development of the undestroyed spores ofbacteria, and this class of bacteria is always the cause of spoilage ingoods of this acidity or lees- Spoilagein Specification of LettersPatent.

Application filed March 29, 1913.

Patented Oct. 2'7, 1914.

Serial No. 757,722.

this case is due to two classes of spore-bearing bacteria. One of theseclasses is anaerobic and produces malodorant gases, said gases causingwhat is known in canning vernacular as swells. The other class producesprincipally lactic acid, and only a very small quantity of gas, notsuflicient to swell the can, and causes what is known in canningvernacular as flat sours This latter class may grow either aerobicallyor anaerobically, and breaks up the sugar into lactic acid. Both ofthese classes of bacteria are normally present in such 'food as has anacidity of less thanone-quarter of one per cent, being present in theform of spores which require a higher degree of heat than the boilingpoint of water to insure their destruction in any primary sterilizingprocess when present in hermetically sealed cans containing food of lessthan one-quarter of one per cent. acidity.

Such foods as are subject to spoilage through the action ofnon-spore-bearing bacteria or through yeasts and molds usually have anacidity of more than one-quarter of one per cent, and it will beunderstood that the process which is hereinafter described is equallyapplicable to both kinds of canned food, whether affected withspore-bearing bacteria or non-spore-bearing bacteria, yeasts and molds.Such canned foods are usually given a primary sterilizing process inboiling water or live steam, etc. at about 212 degrees Fahrenheit.

Having above described the sterilizing processes to which canned i'oodproducts are usually subjected at the cannery, and shown that suchprocesses not only fail in many cases to destroy the bacteria present inthe food, but on the other hand promote their development, I will nowstate how I ropose to effectively destroy the living acteria developedfrom the spores and the nonspore-bearing bacteria softened by theliquid, also the yeasts and molds, and prevent the spoilage of all suchcanned oods.

It is to'be borne in mind that t e character of the original sterilizingprocess to which the canned foods have been subjected is immaterial, andit makes no difference whether the original process was in a closedsteam retort or process kettle, agitating retort systems, calcium baths,oil baths, paraffin baths, insuflicient fractional sterilization,electric sterilization, pressure sterilization or any primary process ofany description.

or boiling water process. My proposed invention may be eflicaciouslyemployed irrespective of any previous process or processes to which thecanned foods may have been subjected, whether such canned foods werehermetically sealed in tin, glass or other hermetical container,providing those primary sterilizations are shown .to have failed to killthe micro-organisms.

My process is as follows: From the warehouse in which the canned foodsare stored as fast as they are packed, a number of cans are takenrepresenting difierent blocks of the freshly stored cans, and thesesamples are placed in an incubator maintained at about bloodtemperature. There they are kept for various lengths of time varying inaccordance with the particular kinds of food and their density. Forinstance, corn, peas, string beans, asparagus and such other foods ascontain a comparatively large quantity of water will be allowed toremain in the incubator for a period of about three (3) days, whilefoods such as squash, pumpkin, baked beans with tomato sauce, spinach,sweet pow tatoes and other products of relatively great density andcontaining but little water will require an incubation period of fromten days to two weeks, to determine whether or not the originalsterilizing process or processes were sufficient to kill or destroy thebacteria in the sealed container. The bac teria, if undestroyed, willgrow more or less rapidly in the incubator where a temperature of bloodheat is maintained, and much faster than in the corresponding blocks ofgoods in the wareroom' where the temperature will be materially less, sothat the undestroyed bacteria will show up in the incubated samplesbefore spoilage has occurred in the wareroom. The spoilage in thewareroom will be sure but gradual at the lower temperature and it is toprevent this spoilage that we proceed in my process with an incubationof the samples from the wareroom.

After incubation, which is the first step of the process, the cans areopened and a quantity of the contents removed therefrom at about thecenter of the container. A suitable microscopic preparation is made ofthis and examined under the microscope with a suitable power for seeingbacteria, yeasts and molds which have developed in the container underthe forced growth in the incubator, and the microscopic examination willshow the presence of such organisms if developed. W hen bacteria arefound it may be definitely ascertained whether or not they are living ordead by inoculating regular bacteria media commonly used inbacteriological laboratories. Tt is essential to know that they areliving. Having thus disclosed the presence ofliving bacteria, in thecanned food the corresponding lots in the ware arrears room are savedfrom spoilage by subjecting them to a boiling water process or itsequivalent for various lengths of time according to the size of the canand the character of the canned food and the density of said food. Thetime for which the cans are allowed to remain in the boiling water bathsvaries from one to two hours, or sufficient to produce a temperature of180 degrees Fahrenheit, or more at the center of the can. Although itmay have been originally necessary to use a temperature far above thatof boiling water in an attempt to thoroughly sterilize the canned food,yet I have discovered that a second process in boiling water after thepresence of living microorganisms have been discovered and (in the timenecessary to secure incubation and microscopic examination), will besufficient to secure complete sterilizatiom'even where a highertemperature up to 250 degrees Fahrenheit or more has originally failedto accomplish the desired end. The reason for this is apparent.

As before stated, in the primary process or processes the spores whichare very hard to kill, which are heat-resisting even to hightemperatures, 2'. 6., such temperatures as may be given withoutafiecting the quality, often survive. The heat held by the can aftersuch sterilization and the liquid in the can serves to further thedevelopment of the spores into bacteria and soften any other organismswhich may have survived a primary process. of any description.Therefore, after the lapse of such time as may be required to make anincubation and microscopic test, these organisms will be in suchphysical shape to be easily destroyed by my secondary process, which isof such comparatively low temperature that it will not injure thequality of the canned food, but will be of sufficient intensity todestroy all such organisms as have survived the primary process. Tt willthus be seen that by testing the contents of a few cans under themicroscope after they have been removed from the incubator as described,my process will prevent the spoilage of large quantities of canned foodswhich may be stored in the warerooms by simply subjecting the same to asecondary process or re-cooking by passing the same through a'bath ofboiling water or its equivalent in order to get a temperature of 180degrees Fahrenheit at the center of the can as previously described.

it will be apparent that owing to the comparatively low temperature ofthe wa" ter, steam or other medium in re-cooking the canned food, thesame will not cause any deterioration in quality, but will effectivelyand completely destroy the microorganisms whether they were originallyspore-bearing or non-spore-bearing.

From the foregoing, it is believed that the nature of my improvedprocess and the manner in which the same is to be practically appliedwill be clearly and fully understood. By means of the same I aim toprevent spoilage of large quantities of canned foods owing to thedevelopment of living bacteria therein, as is now. experienced by nearlyall packers of canned foods.

After the canned foods have been subjected to my improved process, theymay be indefinitely preserved in an edible condition. It is of course tobe understood that it is not essential that the cans be placed in a bathof boiling water, but they may be subjected to heat in any other manner,it being only necessary that the food at the center of the can attain atemperature of approximately 180 degrees to insure the destruction ofall living bacteria therein.

Having thus described the invention, what is claimed is:

1. A. process for preventing the spoilage of previously processed solidor semi-solid foods packed in hermetically sealed containers whichconsists in subjecting representative sample containers to an incubatingheat to develop such bacteria as may be present in the food, thenexamining the food to ascertain'the existence or non-existence ofdeveloped living bacteria therein, whereby, if any bacteria are found,it will be disclosed that undeveloped bacteria exist in the remainingcontainers, from which the samples Were taken, and finally subjectingthe remaining containers to one single re-cook at a temperatureapproximating that of approximately boiling water for a sufficient timeto convey a temperature of 180 degrees Fahrenheit to the center of thecontainers whereby the bacteria are killed.

2. A process for preventing the spoila e of previously processed solidor semi-solid foods packed in hermetically sealed containers whichconsists in subjecting representative sample containers to an incubatingheat for a period of time varying inversely with the fluidity of thefood in the container from three days to two Weeks to develop any livingbacteria in the food, then removing a portion of the food from theapproximate center of the container and examining the same to definitelyascertain the presence of living bacteria, and should such bacteria befound thus disclosing that undeveloped bacteria of a similar characterexist in the remaining bulk of containers, then subjecting the remainingcontainers to a temperature approximating that of boiling water for asuflicient time necessary to convey a temperature of approximately 180Fahrenheit to the center of the containers.

3. A process for preventing the spoilage of solid or semi-solid foodspacked in her metically sealed containers which consists in subjectingsample containers taken from freshly packed goods to an incubation for apredetermined length of time to develop any bacteria present therein,then opening the sample containers, taking a sample from the centerthereof, and examining the same to definitely determine the presence ofliving bacteria and, if living bacteria are found thus disclosing thatlike bacteria exist, in a less developed form, in the remainingcontainers from which the samples were taken, then subjecting saidremaining containers to a boiling Water bath or its equivalent for asufficient time to convey a tem perature of approximately 180 Fahrenheitto the center of the containers.

In testimony whereof I hereunto aflix my signature in the presence oftwo witnesses.

EDWARD W. DUCKWALL,

Witnesses:

A. L. NEHLS, E. R. LONG.

